Terminal, radio communication method, and base station

ABSTRACT

A terminal is disclosed that includes a transmitter that transmits a physical uplink shared channel (PUSCH) and a measurement reference signal (sounding reference signal (SRS)) and a processor that performs sensing and controls to contiguously transmit the PUSCH and the SRS after the sensing. In other aspects, a radio communication method and a base station are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 16/069,579, filed on Jul. 12, 2018, which is anational phase application of PCT/JP2017/004018, filed on Feb. 3, 2017,which claims priority to Japanese Patent Application No. 2016-020217,filed on Feb. 4, 2016. The contents of these applications are herebyincorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a terminal, a radio communicationmethod, and a base station for a next-generation mobile communicationsystem.

BACKGROUND ART

For the universal mobile telecommunications system (UMTS) network, thelong-term evolution (LTE) has been specified for further enhanced datarates and lower delay (see Non-Patent Literature 1). The LTE-A (alsoreferred to as LTE advanced, LTE Rel. 10, 11, or 12) has been specifiedfor achieving even wider bands and higher speed than those of LTE (alsoreferred to as LTE Rel.8 or 9), and the succeeding systems (e.g., futureradio access (FRA), 5^(th) generation mobile communication system (5G),and LTE Rel.13) are under study.

LTE Rel.8 to 12 have been specified assuming exclusive use of frequencybands given to providers (operators) (also referred to as licensedbands). For licensed bands, 800 MHz, 1.7 GHz, 2 GHz or the like is used.

In recent years, the widespread use of smartphones, tablets, or otherhigh-function user terminal (UE) has dramatically increased usertraffic. Further additional frequency bands are required to absorbincreasing user traffic, although there is a limitation on the number ofspectra for licensed bands (licensed spectra).

For this reason, Rel.13 LTE assumes extending the frequency for LTEsystems by using bands of unlicensed spectra (unlicensed bands) whichare non-exclusive to licensed bands (see Non-Patent Literature 2).Examples of assumed unlicensed bands include 2.4-GHz and 5-GHz bands inwhich, for example, Wi-Fi (registered trademark) and Bluetooth(registered trademark) can be used.

In particular, LTE Rel.13 assumes carrier aggregation (CA) of licensedbands and unlicensed bands. Communication using licensed bands togetherwith unlicensed bands in this manner is referred to as license-assistedaccess (LAA). It should be noted that future LAA possibly assumes dualconnectivity (DC) of licensed bands and unlicensed bands and stand-alone(SA) of unlicensed bands.

CITATION LIST Non-Patent Literature [Non-Patent Literature 1]

3GPP TS 36.300 “Evolved Universal Terrestrial Radio Access (E-UTRA) andEvolved Universal Terrestrial Radio Access Network (E-UTRAN); Overalldescription; Stage 2”

[Non-Patent Literature 2]

AT&T, “Drivers, Benefits and Challenges for LTE in Unlicensed Spectrum,”3GPP TSG RAN Meeting #62 RP-131701

SUMMARY OF INVENTION Technical Problem

Communication using an unlicensed band needs to take into considerationother entities that communicate using this unlicensed band (e.g., otheruser terminal). Accordingly, if a scheme of assigning the uplinkresource for the licensed band is applied to an unlicensed band as itis, proper resource assignment in the unlicensed band may not beperformed particularly in uplink (UL) transmission.

An object of the present invention, which has been made to solve thisproblem, is to provide a user terminal, a radio base station, and aradio communication method that provide proper resource assignment incommunication using an unlicensed band.

Solution to Problem

A user terminal according to one embodiment includes: a transmittingsection that transmits a UL signal; and a control section that controlsthe transmitting section to transmit a physical uplink shared channel(PUSCH) and a measurement reference signal (sounding reference signal(SRS)) in accordance with different grants included in a DL signal. Thecontrol section transmits the physical uplink shared channel followingtransmission of the measurement reference signal.

Advantageous Effects of Invention

The present invention provides proper resource assignment incommunication using an unlicensed band.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are diagrams illustrating a radio frame configuration inan unlicensed band.

FIG. 2 is a diagram illustrating a radio frame configuration in anunlicensed band according to the first embodiment.

FIGS. 3A and 3B are diagrams illustrating information (UL subframeconfiguration information) on a UL configuration according to the secondembodiment.

FIGS. 4A and 4B are diagrams for explaining a UL configuration accordingto the third embodiment.

FIG. 5 is a diagram illustrating an example schematic configuration of aradio communication system according to this embodiment.

FIG. 6 is a diagram illustrating an example overall configuration of aradio base station according to this embodiment.

FIG. 7 is a diagram illustrating an example functional structure of aradio base station according to this embodiment.

FIG. 8 is a diagram illustrating an example of the overall configurationof user terminal according to this embodiment.

FIG. 9 is a diagram illustrating an example of the functionalconfiguration of user terminal according to this embodiment.

FIG. 10 is a diagram illustrating an example of the hardwareconfiguration of a radio base station and user terminal according tothis embodiment.

DESCRIPTION OF EMBODIMENTS

A system for running LTE/LTE-A in an unlicensed band (e.g., LAA system)may require an interference control function for coexistence with LTE,Wi-Fi, or other systems of other providers. It should be noted thatsystems for running LTE/LTE-A in unlicensed bands may be collectivelyreferred to as LAA, LAA-LTE, LTE-U, or U-LTE, independently of itsrunning method: CA, DC or SA.

In general, a transmission point (e.g., radio base station (eNB) or userterminal (UE)) that communicates using a carrier in an unlicensed band(which can be referred to as carrier frequency or simply frequency) isbanned from transmitting through the carrier, upon detection of anotherentity (e.g., another user terminal) that communicates using a carrierin that unlicensed band.

For this reason, a transmission point performs listening (listen beforetalk (LBT)) in a timing which is a predetermined period before thetransmission timing. To be specific, a transmission point performing LBTsearches an entire target carrier band (e.g., one component carrier(CC)) in a timing which is a predetermined period before thetransmission timing and determines if another device (e.g., a radio basestation, user terminal, or a Wi-Fi device) is communicating in thatcarrier band.

In this description, listening is to detect/measure whether, before onetransmission point (e.g., a radio base station or user terminal)transmits a signal, another transmission point transmits a signalexceeding a predetermined level (e.g., predetermined power). Listeningperformed by a radio base station and/or user terminal may be referredto as LBT, clear channel assessment (CCA), or carrier sense.

If the fact that no other device is performing communication isconfirmed, the transmission point transmits using that carrier. Forexample, if reception power measured by LBT (reception signal powerduring LBT) is below a predetermined threshold, the transmission pointdetermines that the channel is in the idle state (LBT_(idle)) andconducts transmission. The fact that “a channel is in the idle state”means that the channel is occupied by a particular system, the channelis idle, the channel is clear, or the channel is free.

Meanwhile, upon detection of the fact that another device is partlyusing the target carrier band, the transmission point stops itstransmission processing. For example, upon detection of the fact thatthe reception power of a signal from the other device associated to thisband exceeds a predetermined threshold, the transmission pointdetermines that the channel is in the busy state (LBT_(busy)) and doesnot perform transmission. In the case of LBT_(busy), the channel becomesavailable once its idle state is confirmed in the next LBT. It should benoted that the method of determining the idle state/busy state of thechannel by using LBT is not limited to this.

Frame based equipment (FBE) and load based equipment (LBE) are assumedas LBT mechanisms (schemes). They differ in frame configuration fortransmission and reception, and channel occupation time. FBE, which isalso referred to as category 2, has fixed timings for an LBT-basedtransmission/reception configuration. LBE, which is also referred to ascategory 4, features an LBT-based transmission/reception configurationwhich is unfixed along the time axis and performs LBT depending on thedemand. It should be noted that transmission independent of LBT is alsoreferred to as category 1.

To be specific, FBE, which features fixed frame cycles, is a mechanismthat performs transmission if the channel is available after apredetermined time of carrier sense in a predetermined frame (which mayalso be referred to as LBT time (LBT duration)) and stays in the standbymode until the carrier sense timing in the next frame if the channel isunavailable.

Meanwhile, LBE is a mechanism that follows the extended CCA (ECCA)procedure that extends carrier sense time if the channel is unavailableafter carrier sense (initial CCA), and continues carrier sense until thechannel becomes available. LBE requires random back-off for properlyavoiding collision.

It should be noted that carrier sense time (which may also be referredto as a carrier sense period) is the time (e.g., one symbol length) whenlistening or other processing is carried out to determine if the channelis available so that one LBT result can be obtained.

A transmission point can transmit a predetermined signal (e.g., achannel reservation signal) depending on the LBT result. Here, the LBTresult refers to information (e.g., LBT_(idIe) or LBT_(busy)) that isobtained by LBT and indicates the availability of the channel in thecarrier to which LBT is allocated.

If the transmission point starts transmission while the LBT result isthe idle state (LBT_(idle)), the transmission can be performed skippingLBT for a predetermined period (e.g., 10 to 13 ms). This type oftransmission is referred to as burst transmission, burst, transmissionburst, and the like.

As described above, in the LAA system, the transmission point isprovided with interference control in the same frequency based on theLBT mechanism, thereby avoiding an interference between LAA and Wi-Fiand between LAA systems. Even in the case where each transmission pointis controlled independently by the corresponding operator running theLAA system, LBT allows control operations to be independent of oneanother, thereby reducing interferences.

In the LAA system, user terminal performs radio resource management(RRM) measurement (including reference signal received power (RSRP)measurement) for detecting cells (secondary cells (SCells)) in anunlicensed band. Discovery reference signals (DRSs) are assumed for usein the RRM measurement.

A DRS used in the LAA system may include at least one of asynchronization signal (primary synchronization signal (PSS)/secondarysynchronization signal (SSS)), a cell-specific reference signal (CRS),and a channel state information reference signal (CSI-RS). The DRS istransmitted during a DMTC period (DMTC duration) in a predeterminedcycle (also referred to as discovery measurement timing configurationperiodicity (DMTC cycle)). It should be noted that the DRS may bereferred to as a detection signal, a detection measurement signal, adiscovery signal (DS), an LAA DRS, or an LAA DS.

In the LAA system, user terminal performs CSI measurement using a CRSand/or a CSI-RS (hereinafter referred to as a CRS/CSI-RS) transmittedthrough a cell in an unlicensed band, and sends the measurement resultto the radio base station (CSI reporting). It should be noted that theCRS may be included in each downlink subframe or a CRS forming a DRS.The CSI-RS is a CSI-RS transmitted in a predetermined cycle (e.g., 5 msor 10 ms) and is allocated in addition to a CSI-RS forming a DRS.

In the LAA system, it is also assumed that, upon the success of LBT (inthe idle state), the minimum transmission band width used by thetransmission point is limited to a predetermined bandwidth (e.g., 5 MHzor 4 MHz) or above.

By the way, enhanced LAA (eLAA) according to Rel.14 assumes variousspecifications for achieving UL CA. For example, it is assumed that ameasurement reference signal (sounding reference signal (SRS)) isspecified as a physical uplink shared channel (PUSCH) or an uplinkreference signal. It is also assumed that the specification of an uplinkL1/L2 control channel (physical uplink control channel (PUCCH)) or aphysical random access channel (PRACH) is changed as needed.

Meanwhile, in DL LAA according to Rel.13, LBT can be performed anytimebut DL transmission should be started and ended at limited times. Thesubframe boundaries for a LAA Scell and a Pcell are aligned with eachother. The times when control/data/reference signals start in onesubframe (14 symbols) are limited to the first and eighth symbol(symbols #0 and #7). The times when the transmission ends are limited tothe third, sixth, ninth, 10th, 11th, 12th, and 14th symbols (symbols #2,#5, #8, #9, #10, #11, and #13). In addition, in DL LAA according toRel.13, subframe-by-subframe processing for LTE is continued.

As described above, the times when transmission is started and ended arelimited to simplify a radio base station and user terminal. If theselimited timings are applied to eLAA, there is a risk that a ULtransmission start timing (hereinafter referred to as a “transmissiontiming”) is limited to a subframe boundary or slot boundary. It shouldbe noted that “a transmission timing” is not a time when a signal isactually output but a time when a control signal, a data signal, areference signal, or other meaningful signals is transmitted.

In LTE, since UL transmission time interval (TTI) is set to 1 ms, it isassumed that resource assignment is not efficiently performed due to LBTwhich can be executed anytime. For example, with limited transmissiontimings, it is assumed that the next subframe is used for DL or UL uponthe success of LBT. Here, if an LBT end time is before a boundary (asubframe boundary or slot boundary), regardless of the success of LBT,UL transmission or DL transmission cannot be started immediately, whichmay hinder efficient resource assignment.

Possible cases will be given below.

In LTE, UL transmission is performed using the symbols in the fourthsubframe after the reception of a subframe including a UL grant. Uponreception of a UL grant, user terminal performs LBT before the subframedesignated by the UL grant and, upon the success of LBT, performs ULtransmission through the designated subframe. It should be noted thatthe UL grant may be transmitted through a licensed carrier or anunlicensed carrier.

For example, as illustrated in FIG. 1A, upon the transmission of an ULgrant to user terminal through a subframe #n+1, the user terminalreceiving it performs LBT (UL LBT) before the subframe #n+5 which is thefourth subframe from the subframe #n+1 that involves the transmission ofthe UL grant. Upon the success of LBT (if the channel is in the idlestate), the user terminal performs UL transmission using the subframe#n+5. In the case where this subframe-by-subframe processing is carriedout for UL transmission, as illustrated in FIG. 1A, a signal for ULtransmission is assigned to all the symbols in the subframe #n+5.

Meanwhile, the subframe following the subframe used for UL transmissionby the user terminal is assumed to be used for DL transmission from aradio base station. At this time, the radio base station needs toconduct LBT (DL LBT). However, since the UL transmission signal isassigned to all the symbols in the subframe #n+5 as illustrated in FIG.1A, LBT is performed from the top of the subframe #n+6.

At the success of LBT, the LBT end time is possibly before a boundary ofthe subframe #n+6 or its slot. Accordingly, the radio base station needsto keep outputting a channel reservation signal for keeping the channelavailable until it reaches any of these boundaries. If the channelreservation signal keeps the channel available and it reaches a boundaryof a slot of the subframe #n+6, the radio base station performs DLtransmission by using a symbol after the last slot of the subframe #n+6.

The subframe following the subframe used for UL transmission by the userterminal is assumed to be used for UL transmission from another piece ofuser terminal. FIG. 1B illustrates the case where the other piece ofuser terminal UE #1 performs UL transmission through the subframe #n+6in accordance with the UL grant in the subframe #n+2. However, even ifthe user terminal UE #1 performs LBT before the subframe #n+6, thechannel is determined to be in the busy state because the user terminalUE #0 performs UL transmission in the subframe #n+5; thus, ULtransmission is impossible in the subframe #n+6.

Accordingly, the present inventors have arrived at this presentinvention, focusing on the fact that the efficiency of resourceassignment is improved by a proper UL subframe configuration (ULconfiguration) in an unlicensed band. For example, they have found that,during UL transmission in an unlicensed band, controlling the number ofsymbols to which a resource can be assigned improves the use efficiencyof frequency in the unlicensed band.

One embodiment of the present invention will now be described in detailreferring to the drawings. Although this embodiment describes a carrier(a cell) involving listening as an unlicensed band, this is notnecessarily the case. This embodiment is applicable to both licensedbands and unlicensed bands as long as they correspond to frequencycarriers (cells) involving listening.

(Radio Communication Method)

A radio communication method according to this embodiment supports twoUL subframe configurations: (a) full-subframe transmission in which allthe symbols in a subframe (e.g., in the case of an LTE subframe, 14symbols in it) are used for UL signal assignment and (b) partialsubframe (partial subframe) transmission in which at least one but notall of the symbols in a subframe is used for UL signal assignment (atleast one symbol is not transmitted). This full-subframe transmissioncan be used for UL transmission using a sequence of subframes (bursttransmission). Partial subframe transmission is used for DL transmissionfrom a radio base station through the following subframe or ULtransmission from another piece of user terminal.

Embodiments of the radio communication method will now be explained.

First Embodiment

In the first embodiment, partial subframe transmission is automaticallyapplied to the last subframe for UL transmission. To be specific, userterminal automatically applies partial subframe transmission to the lastsubframe for UL transmission, and assigns a UL signal to the symbols inthis subframe. In UL transmission using burst transmission, the lastsubframe uses partial subframe transmission and the other subframes usefull-subframe transmission. For example, when a single subframe isdesignated by a UL grant, user terminal applies partial subframetransmission to the designated subframe.

For example, as illustrated in FIG. 2, suppose that upon DL transmissionfrom a radio base station, the UL grants for the subframes #n+1 and #n+2designate UL transmission for the user terminal UE #0. To be specific,the UL grant for the subframe #n+1 designates the subframe #n+5 whichcomes after four subframes. The UL grant for the subframe #n+2designates the subframe #n+6 which comes after four subframes.

The user terminal UE #0 performs burst transmission as UL transmission,full-subframe transmission is used for the UL subframe of the subframe#n+5, so that UL signals are assigned to all the symbols. Meanwhile,partial subframe transmission is used for the subframe #n+6, which isthe last subframe for burst transmission, so that UL signals areassigned to at least one but not all of the symbols in the subframe (atleast one symbol in the subframe is not transmitted).

In UL signal assignment with partial subframe transmission, the lastsymbol (the latest symbol along the time axis) or a predetermined numberof the last symbols (a predetermined number of the latest symbols alongthe time axis) in the UL subframe are punctured, and UL signals areassigned to the rest of the symbols. Since the last one or more symbolsin the UL subframe are punctured, a gap in which no UL signals aretransmitted through the subframe is generated.

Referring to FIG. 2, a gap formed in the subframe #n+6 is used toperform LBT so that the next subframe #n+7 can be used. In the drawing,the subframe #n+3 includes a UL grant for the user terminal #1 and thisUL grant designates the subframe #n+7. The user terminal #UE1, whichperforms UL transmission in the subframe #n+7, can perform LBT in thegap formed in the subframe #n+6.

Upon the success of LBT, as illustrated in FIG. 2, the user terminal UE#1 performs UL transmission through the subframe #n+7.

In addition, partial subframe transmission is used for the user terminalUE #1 because the UL transmission through the subframe #n+7 is not bursttransmission. Therefore, a gap is also formed in the subframe #n+7 as inthe subframe #n+6. In the example illustrated in FIG. 2, DL transmissionis performed by the radio base station through the subframe #n+8 orlater. Consequently, the radio base station can perform DL LBT in thegap formed in the subframe #n+7.

As described above, the first embodiment does not need to continuouslyoutput such a long channel reservation signal that occurs in the caseillustrated in FIG. 1A. Further, it can prevent the failure of ULtransmission performed by the user terminal UE #1 through a subframedesignated by a UL grant, due to the busy state of the channel asillustrated in the case in FIG. 1B.

In this manner, the first embodiment employs a proper UL subframeconfiguration (UL configuration) in an unlicensed band, improving theefficiency of resource assignment. This leads to an improvement in theuse efficiency of frequency in the unlicensed band.

For burst transmission, when partial subframe transmission is only usedfor the last subframe and full-subframe transmission is used for theother subframes, a gap formation is prevented in the subframes otherthan the last subframe. If a gap is formed in any of the subframes otherthan the last subframe, this gap may be used by the other user terminalfor its LBT and UL transmission for this user terminal may be aninterrupt.

In this first embodiment, the number of symbols for partial subframetransmission applied to the last subframe may be controlled by controlinformation transmitted from a radio base station. For example, controlinformation contained in downlink control information (DCI) may be usedto designate the number of symbols or update UL subframe configurationinformation (information on the UL configuration) which is preliminarilyloaded to user terminal. Such control information transmission may use anotification scheme according to the second embodiment described below.

Second Embodiment

In the second embodiment, notification of the configuration of eachsubframe in UL transmission is dynamically performed. To be specific,the radio base station dynamically instructs which transmission scheme,full-subframe transmission or partial subframe transmission, is used,through UL subframe configuration information (information on the ULconfiguration) for every subframe for UL transmission. UL subframeconfiguration information may consist of, for example, 1-bit informationillustrated in FIG. 3A or 2-bit information illustrated in FIG. 3B.

UL subframe configuration information illustrated in FIG. 3A is 1-bitinformation. Bit “0” represents X symbols (X is less than 14), and bit“1” represents 14 symbols. Such UL subframe configuration informationcan designate whether each subframe configuration consists of X symbolsor 14 symbols. In particular, for a subframe designated by bit “0” canuse partial subframe transmission with X symbols, and a subframedesignated by bit “1” can use full-subframe transmission with 14symbols.

UL subframe configuration information in FIG. 3B is 2-bit information.“00” represents 11 symbols, “01” represents 12 symbols, “10” represents13 symbols, and “11” represents 14 symbols. Such UL subframeconfiguration information can designate which of the following:full-subframe transmission and partial subframe transmission eachsubframe uses. Further, in partial subframe transmission, it is possibleto designate with which of the following number of symbols: 11, 12, and13, assignment for UL signals is performed.

Controlling the number of symbols for partial subframe transmissionenables control of the gap length for LBT (listening). For example,partial subframe transmission using 11 symbols ensures a gap length ofthree symbols. Similarly, 12 symbols ensure a gap length of two symbols,and 13 symbols ensure a gap length of one symbol. The time that atransmit base station using the next subframe requires for listening forkeeping a channel varies depending on the values of random back-off andcontention window size that the transmit base station uses for LBT.Therefore, with UL subframe configuration information in FIG. 3B, in aradio base station, the gap length required for listening can beindicated according to the LBT parameters applied to the radio stationor user terminal connected thereto, thereby avoiding long-time output ofa channel reservation signal that continues until a subframe boundary orslot boundary.

This 1-bit or 2-bit UL subframe configuration information may benotified from a radio base station to user terminal through ULscheduling DCI. In this case, an existing DCI format 0/4 may be used.Alternatively, a new DCI format (new extended DCI format) for LAA ULscheduling may be defined for used.

Alternatively, UL subframe configuration information may be notifiedthrough common signaling, e.g., a common DCI in the same subframe asscheduling DCI. When user terminal fails to detect the common DCI, a ULsubframe with a predetermined number of symbols (a default number ofsymbols) may be used. For example, any of the bit numbers (two bits)illustrated in FIG. 3B is defined as a default value and resourceassignment for a UL subframe may be performed based on the number ofsymbols designated by this bit number.

Alternatively, UL subframe configuration information may be notifiedthrough higher-layer signaling, for example, RRC signaling. Further,with higher-layer signaling, the number of symbols (X symbols)designated by bit “0” in FIG. 3A may be updated. For example, withhigher-layer signaling, the value X may be designated.

In this manner, like the first embodiment, the second embodiment employsa proper UL subframe configuration (UL configuration) in an unlicensedband, improving the efficiency of resource assignment (FIG. 2). Thisleads to an improvement in the use efficiency of frequency in theunlicensed band. In the second embodiment, in particular, theconfiguration of each subframe for UL transmission is dynamicallynotified to user terminal, thereby providing a proper UL subframeconfiguration that varies dependent on the causes of variations in thetime required for listening, such as the values of random back-off andcontention window size that the transmit base station uses for LBT.

Third Embodiment

The third embodiment relates to transmission of measurement referencesignals (sounding reference signals (SRSs)) serving as uplink referencesignals. In partial subframe transmission used in the first and secondembodiments, the last one or more symbols out of the 14 symbols in a ULsubframe are punctured. In this case, symbols to which an SRS isassigned may be removed, which may decrease the opportunity oftransmitting SRSs. To solve this problem, the third embodiment providesa technique for ensuring the opportunity of transmitting SRSs even ifpartial subframe transmission is used.

To be specific, when UL transmission is scheduled and partial subframetransmission is used, an SRS is transmitted through a symbol just beforea subframe for transmitting a PUSCH. As illustrated in FIG. 4A, an SRSis assigned to the symbol just before the subframe (shortened UL PUSCH)for partial subframe transmission.

This type of SRS transmission may be based on either SRS generation inan uplink pilot timeslot (UpPTS) or SRS generation in a normal subframe.

Transmission of an SRS, serving as an aperiodic SRS, is triggered byDCI. For this reason, when UL LBT is succeeded and the symbol justbefore the subframe for transmitting a PUSCH is available, an SRS istransmitted through this symbol (FIG. 4A). Alternatively, as illustratedin FIG. 4B, the SRS may be transmitted through the last symbol of thesubframe for transmitting the PUSCH. This type of SRS transmission canbe used, for example, when the symbol just before the subframe fortransmitting the PUSCH is not available.

When SRS transmission is triggered, user terminal may determine which ofthe methods of transmitting an SRS illustrated in FIGS. 4A and 4B isused. As illustrated in FIGS. 4A and 4B, the positions of the symbols towhich a demodulation reference signal (DMRS) is assigned are fixed.

As described above, the third embodiment provides a technique forensuring the opportunity of transmitting SRSs even if partial subframetransmission is used.

Fourth Embodiment

A radio communication method according to this embodiment defines, as anew parameter, the number of symbols that can be used for a UL subframe.For this reason, the transport block size (TBS), which is generallydetermined by an instruction given by a modulation and coding scheme(MCS), is preferably taken into consideration. For example, UL transportblock assignment in an LAA Scell is preferably made taking intoconsideration not only a 5-bit MCS field but also the number of symbolsin the available subframe.

To be specific, PUSCH transport block assignment (TBS) for a LAA Scellis made according to the MCS field, PRB number, and the number ofsymbols that can be assigned in PUSCH UL transmission. It should benoted that the number of symbols that can be assigned in PUSCH ULtransmission depends on not only the presence or absence of SRStransmission but also UL subframe configuration information sent from aradio base station.

As described above, the fourth embodiment can provide proper TBS,thereby improving the use efficiency of frequency in an unlicensed band.

As described above, the radio communication method according to thisembodiment controls (performs appropriate setting of) the UL subframeconfiguration (UL configuration) in an unlicensed band, improving theefficiency of resource assignment. Particularly the number of symbolsavailable for resource assignment is controlled, leading to animprovement in the use efficiency of frequency in the unlicensed band.

(Radio Communication System)

The configuration of a radio communication system according to thisembodiment will now be described. This radio communication systememploys a radio communication method according to each of theaforementioned embodiments. It should be noted that the radiocommunication methods according to the embodiments may be used alone orin combination.

FIG. 5 is a diagram illustrating an example schematic configuration of aradio communication system according to this embodiment. A radiocommunication system 1 can employ carrier aggregation (CA) and/or dualconnectivity (DC) that unites a plurality of basic frequency blocks(component carriers) using a system band width for an LTE system as onesection. Moreover, this radio communication system 1 includes radio basestations that can use unlicensed bands ((e.g., LTE-U base stations).

It should be noted that the radio communication system 1 may also bereferred to as SUPER 3G, LTE-Advanced (LTE-A), IMT-Advanced, 4thgeneration mobile communication system (4G), 5th generation mobilecommunication system (5G), or future radio access (FRA).

The radio communication system 1 in FIG. 5 includes a radio base station11 that forms a macro cell C1, and radio base stations 12 (12 a to 12 c)that form small cells C2 which are present inside the macro cell C1 andsmaller than the macro cell C1. User terminal 20 exists in the macrocell C1 and the small cells C2. For example, the macro cells Cl may beused in licensed bands, and the small cells C2 may be used in unlicensedbands (LTE-U). Further, at least one but not all of the small cells maybe used in licensed bands, and the other small cells may be used inunlicensed bands.

The user terminal 20 can be connected to both the radio base station 11and the radio base stations 12. The user terminal 20 is assumed to usethe macro cell C1 and the small cells C2, which use differentfrequencies, at the same time with CA or DC. For example, the radio basestation 11 using a licensed band can transmit assistance information(e.g., downlink signal configuration) on the radio base stations 12(e.g., LTE-U base stations) using an unlicensed band, to the userterminal 20. To achieve CA between a licensed band and an unlicensedband, one radio base station (e.g., the radio base station 11) maycontrol the schedules of licensed band cells and unlicensed band cells.

The user terminal 20 may be connected not to the radio base station 11but to the radio base stations 12. For example, the radio base stations12 using an unlicensed band may be connected to the user terminal 20 ina standalone manner. In this case, the radio base stations 12 controlthe schedules of the unlicensed band cells.

Communication between the user terminal 20 and the radio base station 11may use a carrier supporting a narrow bandwidth (referred to as anexisting carrier or legacy carrier), in a relatively low frequency band(e.g., 2 GHz). Meanwhile, communication between the user terminal 20 andeach radio base station 12 may use a carrier supporting a wide bandwidthor the same carrier as that between the user terminal 20 and the radiobase station 11, in a relatively high frequency band (e.g., 3.5 GHz or 5GHz). It should be noted that the frequency band used by each radio basestation is not limited to this.

The radio base station 11 and each radio base station 12 (or two radiobase stations 12) may be wired to each other (e.g., through an opticalfiber or X2 interface according to the common public radio interface(CPRI)) or connected wirelessly to each other.

The radio base station 11 and the radio base stations 12 are connectedto a higher station apparatus 30 and to a core network 40 via the higherstation apparatus 30. Examples of the higher station apparatus 30include, but should not be limited to, access gateway devices, radionetwork controllers (RNCs), and mobility management entities (MMEs).Each radio base station 12 may be connected to the higher stationapparatus 30 via the radio base station 11.

It should be noted that the radio base station 11 is a radio basestation with a relatively wide coverage and may be referred to as amacro base station, an aggregate node, an eNodeB (eNB), or atransmit/receive point. It should be noted that the radio base station12 is a radio base station with local coverage and may be referred to asa small base station, a micro base station, a pico base station, a femtobase station, a home eNodeB (HeNB), a remote radio head (RRH), or atransmit/receive point. When the radio base stations 11 and 12 are notdistinguished from each other, they are collectively referred to as aradio base station 10. Radio base stations 10 sharing the sameunlicensed band are preferably in synchronization with each other alongthe time axis.

Each user terminal 20 supports LTE, LTE-A, and other communicationsystems and may be a mobile communication terminal or a land-linecommunication terminal.

The radio communication system 1 uses orthogonal frequency divisionmultiple access (OFDMA) for downlink and single-carrier frequencydivision multiple access (SC-FDMA) for uplink as radio access schemes.OFDMA is a multi-carrier transfer system in which a frequency band isdivided into a plurality of narrow frequency bands (sub-carriers) anddata is mapped to each sub-carrier for communication. SC-FDMA is asingle-carrier transfer system in which the system band width is dividedinto bands each consisting of one or a sequence of resource blocks foreach equipment piece and a plurality of equipment pieces use differentbands, thereby reducing an interference between the equipment pieces. Itshould be noted that the combination of uplink and downlink radio accesssystems is not necessarily like this.

In the radio communication system 1, the downlink channels are physicaldownlink shared channels (PDSCHs) shared among the user terminal 20,physical broadcast channels (PBCHs), and downlink L1/L2 controlchannels, for example. A PDSCH may also be referred to as a downlinkdata channel. User data, higher layer control information, systeminformation blocks (SIBs), and the like are transmitted through PDSCHs.Master information blocks (MIBs) are transmitted through PBCHs.

Downlink L1/L2 control channels include physical downlink controlchannels (PDCCHs), enhanced physical downlink control channels(EPDCCHs), physical control format indicator channels (PCFICHs), andphysical hybrid-ARQ indicator channels (PHICHs). Downlink controlinformation (DCI) including PDSCH and PUSCH scheduling information istransmitted through PDCCHs. Control format indicator (CFI) indicating anOFDM symbol number used for a PDCCH is transmitted through a PCFICH.Arrival confirmation information (ACK/NACK) related to HARQ for a PUSCHis transmitted through a PHICH. Like a PDCCH, an EPDCCH is subjected tofrequency division multiplexing with a PDSCH and used for DCItransmission.

In the radio communication system 1, the uplink channels are physicaluplink shared channels (PUSCHs) shared among the user terminal 20, anduplink L1/L2 control channels (physical uplink control channels(PUCCHs)), and physical random access channels (PRACHs), for example. APUSCH may be referred to as an uplink data channel. User data and upperlayer control information are transmitted through PUSCHs.

In addition, downlink radio quality information (channel qualityindicator (CQI)) and arrival confirmation information (ACK/NACK) aretransmitted through a PUCCH. A random access preamble for establishingconnection with a cell is transmitted through a PRACH.

Downlink reference signals in the radio communication system 1 includecell-specific reference signals (CRSs), channel stateinformation-reference signals (CSI-RSs), demodulation reference signals(DMRS), and detection and/or measurement reference signals (discoveryreference signals (DRSs)). Uplink reference signals in the radiocommunication system 1 include measurement reference signals (soundingreference signals (SRSs)) and demodulation reference signals (DMRSs). Itshould be noted that a DMRS may be referred to as a userterminal-specific reference signal (a UE-specific reference signal).These are not all the transmitted reference signals.

<Radio Base Station>

FIG. 6 is a diagram illustrating an example overall configuration of aradio base station according to this embodiment. The radio base station10 includes a plurality of transmitting/receiving antennas 101,amplifying sections 102, transmitting/receiving sections 103, a basebandsignal processing section 104, a call processing section 105, and atransfer path interface 106. It should be noted that it includes one ormore transmitting/receiving antennas 101, one or more amplifyingsections 102, and one or more transmitting/receiving sections 103.

User data transmitted from the radio base station 10 to the userterminal 20 through a downlink channel is fed from the higher stationapparatus 30 to the base band signal processing section 104 through thetransfer path interface 106.

The base band signal processing section 104 subjects user data to packetdata convergence protocol (PDCP) layer processing, user datadivision/combination, transmission processing for an RLC layer, such astransmission processing for radio link control (RLC) retransmissioncontrol, medium access control (MAC) retransmission control (e.g.,hybrid automatic repeat request (HARQ) transmission processing),scheduling, transmission format selection, channel coding, inverse fastFourier transform (IFFT) processing, and pre-coding processing or othertransmission processing, and transmits it to each transmitting/receivingsection 103. Downlink control signals are subjected to transmissionprocessing, such as channel coding and inverse fast Fourier transform,and then are transferred to each transmitting/receiving section 103.

Each transmitting/receiving section 103 inverts downlink signals, whichare pre-coded for each antenna and output from the base band signalprocessing section 104, to the radio frequency band. Radio-frequencysignals which are frequency-inverted in the transmitting/receivingsection 103 are amplified by the amplifying section 102 and thentransmitted from the transmitting/receiving antenna 101.

The transmitting/receiving section 103 can transmit and receive uplinkand/or downlink (hereinafter referred to as uplink/downlink) signals inan unlicensed band. It should be noted that the transmitting/receivingsection 103 may be able to transmit and receive uplink/downlink signalsin a licensed band. Each transmitting/receiving section 103 is atransmitter/receiver, transmitting/receiving circuit, or atransmitting/receiving device based on common understanding within thetechnical field of the present invention. It should be noted that thetransmitting/receiving section 103 may be a combinationtransmitting/receiving section or consist of a transmitting section anda receiving section.

As for uplink signals, radio-frequency signals received at thetransmitting/receiving antenna 101 are amplified in the amplifyingsection 102. The transmitting/receiving section 103 receives uplinksignals amplified in the amplifying section 102. Thetransmitting/receiving section 103 frequency-inverts the receivedsignals to baseband signals and feed them to the baseband signalprocessing section 104.

In the base band signal processing section 104, user data in thereceived uplink signals is subjected to fast Fourier transform (FFT)processing, inverse discrete Fourier transform (IDFT) processing, errorcorrection decoding, reception processing for MAC retransmissioncontrol, and reception processing for RLC layers and PDCP layers, andthen transferred to the higher station apparatus 30 through the transferpath interface 106. The call processing section 105 performs callprocessing, such as communication channel allocation and release,management of the radio base station 10, and management of the radioresource.

The transfer path interface 106 transmits/receives signals to/from thehigher station apparatus 30 via a predetermined interface. The transferpath interface 106 may transmit/receive signals to/from another radiobase station 10 through a base station to base station interface (e.g.,an optical fiber or X2 interface according to a common public radiointerface (CPRI)) (backhaul signaling).

It should be noted that the transmitting/receiving section 103 transmitsdownlink signals to user terminal 20 through at least an unlicensedband. For example, the transmitting/receiving section 103 transmits DCI(an UL grant) for assigning a PUSCH to user terminal 20, and DCI (DLassignment) for assigning a PDSCH to user terminal 20.

It should be noted that the transmitting/receiving section 103 receivesuplink signals to user terminal 20 through at least an unlicensed band.For example, the transmitting/receiving section 103 receives the DCI(the UL grant) for assigning a PUSCH from user terminal 20. In addition,the transmitting/receiving section 103 may receive the results of RRMmeasurement and/or CSI measurement (e.g., A-CSI) from user terminal 20in a licensed band and/or unlicensed band.

FIG. 7 is a diagram illustrating an example of the functional structureof a radio base station according to this embodiment. It should be notedthat FIG. 7 mainly illustrates function blocks which are characteristicsof this embodiment, and the radio base station 10 includes otherfunction blocks required for radio communication. As illustrated in FIG.7, the baseband signal processing section 104 includes a control section(scheduler) 301, a transmission signal generating section 302, a mappingsection 303, a reception signal processing section 304, and ameasurement section 305.

The control section (scheduler) 301 controls the entire radio basestation 10. It should be noted that when one control section (scheduler)301 performs scheduling for licensed bands and unlicensed bands, thecontrol section 301 controls communication of licensed band cells andunlicensed band cells. The control section 301 can be a controller, acontrol circuit, or a control device based on common understandingwithin the technical field of the present invention.

The control section 301 controls, for example, generation of downlinksignals by the transmission signal generating section 302 and assignmentof downlink signals by the mapping section 303. The control section 301also controls signal reception processing in the reception signalprocessing section 304 and signal measurement in the measurement section305.

The control section 301 controls scheduling, generation, mapping,transmission, and the like of downlink signals (e.g., systeminformation, PDCCHs/EPDCCHs and PDSCHs for transmitting DCI, downlinkreference signals, synchronization signals). In addition, the controlsection 301 controls LBT (listening) performed by the measurementsection 305 and then controls transmission of downlink signals to thetransmission signal generating section 302 and the mapping section 303in accordance with the LBT results.

The control section 301 may control the transmitting/receiving section103 and the like such that, for user terminal subjected to listeningbefore UL transmission, the radio base station receives a UL signalassigned to disable transmission of at least one symbol in a ULsubframe, in accordance with the results of listening.

Under control by the control section 301, in user terminal, controlinformation (first embodiment) that defines the number of symbols forpartial subframe transmission may be transmitted. Under control by thecontrol section 301, which transmission scheme, full-subframetransmission or partial subframe transmission, is used may bedynamically indicated for UL subframe configuration information(information on UL configuration) every subframe during UL transmission(second embodiment). Control by the control section 301 may allow suchUL subframe configuration information to be transmitted to user terminalthrough at least one of higher-layer signaling and a DL control signaland a common DL control signal for UL scheduling.

Under control by the control section 301 during partial subframetransmission, an SRS assigned to one symbol (third embodiment) may bereceived and channel estimation may be performed based on this signal.Under control by the control section 301, in user terminal, UL transportblock assignment may be performed based on an MCS field, a PRB number,and the number of symbols that can be assigned in PUSCH UL transmission(fourth embodiment).

The transmission signal generating section 302 generates downlinksignals in accordance with instructions from the control section 301 andfeeds them to the mapping section 303. The transmission signalgenerating section 302 can be a signal generator, a signal generatingcircuit, or a signal generating device based on common understandingwithin the technical field of the present invention.

The transmission signal generating section 302 generates, for example,assignment information for downlink resources (DL assignment) andassignment information for uplink resources (UL grants) in accordancewith instructions from the control section 301. Downlink data signalsare subjected to coding and demodulation in accordance with the codingrate, the demodulation scheme, and the like determined in accordancewith the results of CSI measurement in each piece of user terminal 20.The transmission signal generating section 302 also generates DRSsincluding PSSs, SSSs, CRSs, and CSI-RSs.

The mapping section 303 maps a downlink signal generated in thetransmission signal generating section 302 to a predetermined radioresource in accordance with an instruction from the control section 301and feeds the result to the transmitting/receiving section 103. Themapping section 303 can be a mapper, a mapping circuit, or a mappingdevice based on common understanding within the technical field of thepresent invention.

The reception signal processing section 304 subjects reception signalssent from the transmitting/receiving section 103 to reception processing(e.g., demapping, demodulation, and decoding). Here, a reception signalis, for example, an uplink signal transmitted from user terminal 20. Thereception signal processing section 304 can be a signal processor, asignal processing circuit, or a signal processing device based on commonunderstanding within the technical field of the present invention.

The reception signal processing section 304 feeds information decoded inreception processing to the control section 301. For example, uponreception of a PUCCH including HARQ-ACK, it feeds HARQ-ACK to thecontrol section 301. In addition, the reception signal processingsection 304 feeds reception signals and signals resulting from receptionprocessing to the measurement section 305.

The measurement section 305 performs measurement related to receivedsignals. The measurement section 305 can be a measure, a measurementcircuit, or a measurement device based on common understanding withinthe technical field of the present invention.

The measurement section 305 performs LBT through a carrier (e.g., anunlicensed band) selected for LBT (listening), in accordance with aninstruction from the control section 301, and then feeds the LBT results(e.g., determination of in which channel state (idle or busy) it is) tothe control section 301.

In addition, the measurement section 305 may measure, for example, thereception power (e.g., reference signal received power (RSRP)),reception quality (e.g., reference signal received quality (RSRQ)), andchannel states of received signals. The measurement results may be sentto the control section 301.

<User Terminal>

FIG. 8 is a diagram illustrating an example of the overall configurationof user terminal according to this embodiment. The user terminal 20includes a plurality of transmitting/receiving antennas 201, amplifyingsections 202, transmitting/receiving sections 203, a baseband signalprocessing section 204, and an application section 205. It should benoted that it includes one or more transmitting/receiving antennas 201,one or more amplifying sections 202, and one or moretransmitting/receiving sections 203.

Radio-frequency signals received at the transmitting/receiving antennas201 are amplified in the amplifying sections 202. Eachtransmitting/receiving section 203 receives downlink signals amplifiedin the amplifying section 202. The transmitting/receiving section 203frequency-inverts the received signals to baseband signals and feed themto the baseband signal processing section 204. Thetransmitting/receiving section 203 may be able to transmit and receiveuplink/downlink signals in an unlicensed band. It should be noted thatthe transmitting/receiving section 203 may be able to transmit andreceive uplink/downlink signals in a licensed band.

Each transmitting/receiving section 203 is a transmitter/receiver,transmitting/receiving circuit, or a transmitting/receiving device basedon common understanding within the technical field of the presentinvention. It should be noted that the transmitting/receiving section203 may be a combination transmitting/receiving section or consist of atransmitting section and a receiving section.

The baseband signal processing section 204 subjects input basebandsignals to reception processing, such as FFT processing, errorcorrection decoding, and retransmission control. Downlink user data istransferred to the application section 205. The application section 205performs processing related to layers higher than physical layers andMAC layers. Broadcast information in downlink data is also transferredto the application section 205.

Meanwhile, uplink user data is input from the application section 205 tothe baseband signal processing section 204. The baseband signalprocessing section 204 performs retransmission control transmissionprocessing (e.g., transmission processing of HARQ), channel coding,pre-coding, discrete Fourier transform (DFT) processing, inverse fastFourier transform (IFFT) processing, and the like, and the results aretransferred to each transmitting/receiving section 203. Eachtransmitting/receiving section 203 inverts a baseband signal, which isoutput from the base band signal processing section 204, to aradio-frequency signal and transfers it. The radio-frequency signalwhich is frequency-inverted by the transmitting/receiving section 203 isamplified by the amplifying section 202 and then transmitted through thetransmitting/receiving antenna 201.

The transmitting/receiving section 203 receives downlink signals from aradio base station 10 in at least an unlicensed band. For example, thetransmitting/receiving section 203 receives measurement referencesignals in an unlicensed band.

The transmitting/receiving section 203 transmits uplink signals to aradio base station 10 in at least an unlicensed band. For example, thetransmitting/receiving section 203 may transmit a PUSCH by using anuplink resource assigned with DCI (an UL grant). Thetransmitting/receiving section 203 may transmit CSI designated by anA-CSI trigger in the DCI (UL grant).

FIG. 9 is a diagram illustrating an example of the functionalconfiguration of user terminal according to this embodiment. It shouldbe noted that FIG. 9 mainly illustrates function blocks which arecharacteristics of this embodiment, and the user terminal 20 includesother function blocks required for radio communication. As illustratedin FIG. 9, the baseband signal processing section 204 in the userterminal 20 includes at least a control section 401, a transmissionsignal generating section 402, a mapping section 403, a reception signalprocessing section 404, and a measurement section 405.

The control section 401 controls the entire user terminal 20. Thecontrol section 401 can be a controller, a control circuit, or a controldevice based on common understanding within the technical field of thepresent invention.

The control section 401 controls, for example, generation of uplinksignals by the transmission signal generating section 402 and assignmentof uplink signals by the mapping section 403. The control section 401also controls downlink signal reception processing in the receptionsignal processing section 404 and signal measurement in the measurementsection 405.

The control section 401 acquires downlink signals transmitted from theradio base station 10 (e.g., PDCCHs/EPDCCHs, PDSCHs, downlink referencesignals, and synchronization signals), from the reception signalprocessing section 404. The control section 401 controls generation ofuplink signals (e.g., PUCCHs and PUSCHs) in accordance with DCIcontained in PDCCHs/EPDCCHs (downlink control signals) and the resultsof demodulation of PDSCHs (downlink data signals).

The control section 401 may control UL signal assignment such thatlistening is performed before UL signal transmission and transmission ofat least one symbol in a UL subframe is disabled in accordance with theresults of the listening. When a UL signal is transmitted in a sequenceof UL subframes, the control section 401 may control UL signalassignment such that transmission of at least one symbol in the last ULsubframe is disabled.

For example, under control by the control section 401, the last subframefor UL transmission automatically uses partial subframe transmission andan UL signal is assigned to symbols in this subframe (first embodiment).In UL transmission using burst transmission, the last subframe usespartial subframe transmission and the other subframes use full-subframetransmission under control by the control section 401. When a singlesubframe is designated by a UL grant, the designated subframe usespartial subframe transmission under control by the control section 401.

Under control by the control section 401, a transmission scheme offull-subframe transmission or partial subframe transmission is usedevery subframe during UL transmission in accordance with UL subframeconfiguration information (information on UL configuration) sent from aradio base station (second embodiment). The control section 401 maycontrol the number of symbols for partial subframe transmission inaccordance with UL subframe configuration information so that the gaplength for LBT (listening) can be controlled.

In addition, under control by the control section 401, the opportunityof transmitting SRSs may be ensured even if partial subframetransmission is used (third embodiment). For example, when a symbol justbefore a subframe for transmitting a PUSCH is available, under controlby the control section 401, an SRS may be transmitted through thissymbol or the last symbol of the subframe for transmitting the PUSCH.

Under control by the control section 401, UL transport block assignmentmay be performed based on an MCS field, a PRS number, and the number ofsymbols that can be assigned in PUSCH UL transmission (fourthembodiment).

The control section 401 controls the reception signal processing section404 and the measurement section 405 such that RRM measurement and/or CSImeasurement is performed using a measurement reference signal in anunlicensed band. It should be noted that RRM measurement may beperformed using DRSs. Further, the measurement reference signal may beCSI included in a CRS, a CSI-RS, or a DRS, or a CSI-RS.

The transmission signal generating section 402 generates uplink signals(e.g., PUSCHs, PUCCHs, and uplink reference signals) in accordance withinstructions from the control section 401 and feeds them to the mappingsection 403. The transmission signal generating section 402 can be asignal generator, a signal generating circuit, or a signal generatingdevice based on common understanding within the technical field of thepresent invention. For example, the control section 401 instructs thetransmission signal generating section 402 to generate a PUSCH when thedownlink control signal transmitted from the radio base station 10includes DCI (an UL grant) addressed to user terminal 20.

The mapping section 403 maps an uplink signal generated in thetransmission signal generating section 402 to a radio resource inaccordance with an instruction from the control section 401 and feedsthe result to the transmitting/receiving section 203. The mappingsection 403 can be a mapper, a mapping circuit, or a mapping devicebased on common understanding within the technical field of the presentinvention.

The reception signal processing section 404 subjects reception signalssent from the transmitting/receiving section 203 to reception processing(e.g., demapping, demodulation, and decoding). Here, the receptionsignal is, for example, a downlink signal transmitted from the radiobase station 10. The reception signal processing section 404 can be asignal processor, a signal processing circuit, or a signal processingdevice based on common understanding within the technical field of thepresent invention. The reception signal processing section 404 may be areceiving section according to the present invention.

The reception signal processing section 404 feeds information decoded inreception processing to the control section 401. The reception signalprocessing section 404 feeds, for example, broadcast information, systeminformation, RRC signaling, and DCI to the control section 401. Inaddition, the reception signal processing section 404 feeds receptionsignals and signals resulting from reception processing to themeasurement section 405.

The measurement section 405 performs measurement related to receivedsignals. The measurement section 405 can be a measure, a measurementcircuit, or a measurement device based on common understanding withinthe technical field of the present invention.

The measurement section 405 may perform LBT through a carrier (e.g., anunlicensed band) selected for LBT, in accordance with an instructionfrom the control section 401. The measurement section 405 may feed theLBT result (e.g., determination of which channel state (idle or busy) itis) to the control section 401.

The measurement section 405 performs RRM measurement and CSI measurementin accordance with an instruction from the control section 401. Forexample, the measurement section 405 performs CSI measurement by using ameasurement reference signal (a CRS, a CSI-RS, a CRS including a DRS, ora CSI-RS for CSI measurement in a DRS transmission subframe). Themeasurement results are output to the control section 401 and thentransmitted from the transmitting/receiving section 103 through a PUSCHor PUCCH.

(Hardware Configuration)

It should be noted that the block diagrams used for describing theaforementioned embodiments illustrate one function as one block. Thesefunction blocks (configuration parts) are achieved by a givencombination of hardware and/or software. Each function block can beachieved by any means. In particular, each function block may beachieved by physically combined one device or multiple devices,specifically, two or more physically separated devices wired orconnected wirelessly.

For example, a radio base station, user terminal, and other componentsaccording to one embodiment of the present invention may function as acomputer for processing in a radio communication method of the presentinvention. FIG. 10 is a diagram illustrating an example of the hardwareconfiguration of a radio base station and user terminal according to oneembodiment of the present invention. The aforementioned radio basestation 10 and the user terminal 20 may be physically configured as acomputer device including a processor 1001, a memory 1002, a storage1003, a communication device 1004, an input device 1005, an outputdevice 1006, and a bus 1007.

In the description below, the term “device” can be replaced with circuitor unit. The hardware configuration of the radio base station 10 and theuser terminal 20 may include one or more devices illustrated in thedrawings or include not all these devices.

The functions of the radio base station 10 and the user terminal 20 arecomposed of the processor 1001, the memory 1002, and other hardwareinstalled with predetermined software (programs) and achieved by thefact that the processor 1001 performs computation, the communicationdevice 1004 provides communication, and data reading and/or writing inthe memory 1002 and the storage 1003 is controlled.

The processor 1001 entirely controls the computer by operating, anoperating system. The processor 1001 may be a central processing unit(CPU) including an interface with peripheral devices, a control device,a computing device, and a register. For example, the aforementionedbaseband signal processing section 104 (204), the call processingsection 105, and other sections may be achieved by the processor 1001.

The processor 1001 reads programs (program codes), software modules, anddata from the storage 1003 and/or the communication device 1004 andsends them to the memory 1002, and various processing is carried out inaccordance with them. The programs are programs for instructing thecomputer to carry out at least part of the operations explained in theaforementioned embodiments. For example, the control section 401 in theuser terminal 20 may be achieved by control programs which are stored inthe memory 1002 and operate with the processor 1001. The other functionblocks may also be operated in the same manner.

The memory 1002 is a computer-readable recording medium, for example, atleast one of read only memory (ROM), erasable programmable ROM (EPROM),and random access memory (RAM). The memory 1002 may also be referred toas a register, cash, or main memory (main storage device). The memory1002 can store programs (program codes), software modules, and the likethat can be executed for implementing a radio communication methodaccording to one embodiment of the present invention.

The storage 1003 may be a computer-readable recording medium, forexample, at least one of compact disc ROM (CD-ROM) or other opticaldiscs, hard disc drives, flexible discs, magneto-optical discs, flashmemory. The storage 1003 may also be referred to as an auxiliary memorydevice.

The communication device 1004 is hardware (transmission/receptiondevice) for communication between computers via wires and/or a radionetwork, e.g., a network device, a network controller, a network card,or a communication module. For example, the aforementionedtransmitting/receiving antenna 101 (201), amplifying section 102 (202),transmitting/receiving section 103 (203), transfer path interface 106,and the like may be achieved by the communication device 1004.

The input device 1005 is an input device receiving inputs from externaldevices (e.g., keyboard and mouse). The output device 1006 is an outputdevice producing outputs to external devices (e.g., display andspeaker). It should be noted that the input device 1005 and the outputdevice 1006 may be integrated into one piece (e.g., touchscreen).

The processor 1001, the memory 1002, and other devices are connected toeach other by the bus 1007 for information communication. The bus 1007may be a single bus or different buses for different devices.

The radio base station 10 and the user terminal 20 may include amicroprocessor, a digital signal processor (DSP), an applicationspecific integrated circuit (ASIC), a programmable logic device (PLD), afield programmable gate array (FPGA), and other hardware, and part orall of each function block may be achieved by the hardware. For example,the processor 1001 may contain at least one of these pieces of hardware.

It should be noted that terms described in this specification and/or theterms necessary for understanding of this specification may be replacedwith terms having the same or similar meanings. For example, “channel”and/or “symbol” may be replaced with “signal (signaling)”. “Signal” maybe replaced with “message”. “Component carrier (CC)” may be referred toas “cell”, “frequency carrier”, or “carrier frequency”.

A radio frame may consist of one or more periods (frames) in the timedomain. The at least one or more periods (frames) forming the radioframe may be referred to as “subframe”. A subframe may consist of one ormore slots in the time domain. A slot may consist of one or more symbols(e.g., OFDM symbols and SC-FDMA symbols) in the time domain.

A radio frame, a subframe, a slot, and a symbol represent time sectionsduring signal transmission. A radio frame, a subframe, a slot, and asymbol may have alternative names. For example, one subframe may bereferred to as a transmission time interval (TTI), a sequence ofsubframes as a TTI, and one slot as a TTI. To be specific, a subframe orTTI may be a subframe (1 ms), a period shorter than 1 ms (e.g., 1 to 13symbols), or a period longer than 1 ms in existing LTE.

Here, a TTI refers to, for example, a minimum time section in schedulingfor radio communication. For example, in an LTE system, a radio basestation performs scheduling for TTI-based assignment of a radio resource(e.g., a frequency band width or transmission power that can be used foreach piece of user terminal) to each piece of user terminal. It shouldbe noted that the definition of TTI is not limited to this.

A 1-ms TTI may be referred to as, for example, a regular TTI (a TTIaccording to LTE Rel.8-12), a normal TTI, a long TTI, a regularsubframe, a normal subframe, or a long subframe. A TTI shorter than aregular TTI may be referred to as a short TTI or a short subframe.

A resource block (RB) is a resource assignment section in the timedomain and the frequency domain and may include a sequence of one ormore sub-carriers in the frequency domain. An RB may include one or moresymbols in the time domain and may have a length of one slot, onesub-frame, or one TTI. One TTI and one sub-frame may each consist of oneor more resource blocks. It should be noted that an RB may be referredas, for example, a physical resource block (physical RB or PRB), a PRBpair, and an RB pair.

A resource block may consist of one or more resource elements (REs). Forexample, one RE may be a radio resource of one sub-carrier and onesymbol.

It should be noted that the aforementioned configurations of radioframe, sub-frame, slot, and symbol are illustrative only. For example,the number of sub-frames included in a radio frame, the number of slotsincluded in a sub-frame, the number of symbols and RBs included in aslot, the number of sub-carries included in an RB, and the number ofsymbols in a TTI, the symbol length, and the cyclic prefix (CP) lengthcan be variously modified.

Information and parameters described in this specification may berepresented by absolute values, values relative to predetermined values,or other corresponding information. For example, a radio resource may beindicated by a predetermined index.

Information and signals described in this specification may be expressedby any of different techniques. For example, data, instructions,commands, information, signals, bits, symbols, and chips mentionedthroughout the above description may be represented by voltage, current,electromagnetic waves, magnetic fields or magnetic particles, opticalfields or photons, or any combination thereof.

Software, instructions, and information may be transmitted and receivedvia a transmission medium. For example, when software is transmittedfrom websites, servers, or other remote sources through wire connectiontechnology (coaxial cables, optical fiber cables, twisted pair cablesand digital subscriber line (DSL)) and/or radio technology (e.g.,infrared rays and microwaves), the wire connection technology and/or theradio technology is contained in the definition of a transmissionmedium.

A radio base station in this specification may be replaced with userterminal. For example, the embodiments of the present invention may beapplied to a configuration in which communication between a radio basestation and user terminal is replaced with device-to-device (D2D)communication between a plurality of user terminal pieces. In this case,the user terminal 20 may have the same function as the radio basestation 10. The terms “uplink” and “downlink” may be replaced with“side”. For example, “uplink channel” may be replaced with “sidechannel”.

Similarly, user terminal in this specification may be replaced with aradio base station. In this case, the radio base station 10 may have thesame function as the user terminal 20.

The embodiments in this specification can be used alone or incombination or can be switched in actual use. In addition, predeterminedinformation notification (e.g., the notification “being X”) is performednot only explicitly but also implicitly (e.g., by not performing thispredetermined information notification).

Information notification is not necessarily performed by the methodsexplained in the embodiments in this specification and may be performedby any other methods. For example, information notification may beperformed by physical layer signaling (e.g., downlink controlinformation (DCI), uplink control information (UCI)), higher-layersignaling (e.g., radio resource control (RRC) signaling, broadcastinformation (master information block (MIB), and system informationblock (SIB)), and medium access control (MAC) signaling), or othersignals, or any combination thereof. RRC signaling may be referred to asan RRC message and may be, for example, an RRC connection setup message,an RRC connection reconfiguration message, or the like. MAC signalingmay be sent through, for example, a MAC control element (MAC controlelement (CE)).

The embodiments described in this specification may be applied tosystems using long term evolution (LTE), LTE-advanced (LTE-A),LTE-beyond (LTE-B), SUPER 3G, IMT-Advanced, 4th generation mobilecommunication system (4G), 5th generation mobile communication system(5G), future radio access (FRA), New-radio access technology (RAT),CDMA2000, ultra mobile broadband (UMB), IEEE 802.11 (Wi-Fi(registeredtrademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20,ultra-wideband (UWB), Bluetooth (registered trademark), and otherappropriate radio communication methods, and/or next-generation systemsextended based on them.

The processes, sequences, and flow charts according to the embodimentsin this specification may be changed in a consistent way. For example,the methods described in this specification suggests various steps in anillustrative order and does not exclusively suggest this particularorder.

The present invention has been described in detail but it is clear tothose skilled in the art that the present invention should not belimited to the embodiments described in this specification. For example,these embodiments may be used alone or in combination. The presentinvention can be implemented in the forms of embodiments amended ormodified without departing from the spirit and scope of the inventiondefined by the claims. Therefore, the description in this specificationis used for giving examples and does not impose any limits to thepresent invention.

1. A terminal comprising: a transmitter that transmits a physical uplinkshared channel (PUSCH) and a measurement reference signal (soundingreference signal (SRS)); and a processor that performs sensing andcontrols to contiguously transmit the PUSCH and the SRS after thesensing.
 2. The terminal according to claim 1, wherein the processorcontrols to contiguously transmit the PUSCH and the SRS in atransmission burst.
 3. The terminal according to claim 2, wherein theprocessor controls to transmit the PUSCH following transmission of themeasurement reference signal.
 4. The terminal according to claim 2,wherein the processor controls to transmit the measurement referencesignal following transmission of the PUSCH.
 5. A radio communicationmethod for a terminal, the method comprising: transmitting a physicaluplink shared channel (PUSCH) and a measurement reference signal(sounding reference signal (SRS)); performing sensing; and controllingto contiguously transmit the PUSCH and the SRS after the sensing.
 6. Abase station comprising: transmitter that transmits, to a terminal, asignal for transmitting at least one of a physical uplink shared channel(PUSCH) and a measurement reference signal (sounding reference signal(SRS)); and receiver that receives the PUSCH and the measurementreference signal; wherein the terminal performs sensing and contiguouslytransmits the PUSCH and the SRS after the sensing.